Production of sheet and strip material



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PRODUCTION OF SHEET AND STRIP MATERIAL Filed Oct. 10, 1950 2 Sheets-Sheet 2 E /34 gal Q33 lnvgmolzs; w wwwy flue;

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Patented June 15, 1954 UNITED F'I'ENT OFFICE Wilfrid C. F. Hessenberg and Raymond B. Sims,

London, England,

and Steel Rcsear England, a British c assignors to The Britishlron ch Association, London, ompany Application October 10, 1950, Serial No. 189,406

Claims priority, application Great Britain,

October 11, 1949 Claims.

The present invention relates to the production of material in the form of sheet or strip either by rolling or by drawin through dies of. the kmd having opposing die surfaces whose separation is adjustable.

In such production the material enterin the reducing member, as the Work rolls or die will be referred to hereafter, may vary in dimensions and other properties along its length and across its width as the result of previous treatment. In known rolling or drawin processes, these variations cause changes in the thickness of the material leaving the reducing member whilst further changes in thickness may be imposed by variations in the conditions of rolling or drawing.

One object of the present invention is to provide a new or improved method of controllin the thickness of the sheet or strip produced so that the outgoing thickness of the material is substantially constant.

According to the invention there is provided the method of producin material in the form of sheet or strip either by rolling or by drawing through dies of the kind specified, in which the separating force between the rolls or dies is maintained substantially constant by continuous adjustment of the tension applied to the material.

This method depends on the fact that if the separating force varies then the thickness of the material leaving the reducing member will vary similarly, Moreover if tension is applied to the material entering or leaving the reducing member then the separating force will be diminished. Thus by continuously adjusting the tension in the material in such a way as to keep the separating force as nearly as possible constant the thickness of the outgoing material may be substantially uniform. along its length.

Broadly, the apparatus for performing the method of the invention comprises means for applying tension to the material enterin or leaving the work rolls or die, and control means responsive to the separating force between the work rolls or opposing die surfaces, said control means bein adapted to contro1 said tension applying means for adjusting the applied tension to maintain said separating force substantially constant.

Two embodiments of apparatus for performing the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings in which Figure l a plan view of the apparatus of the first embodiment, whilst Figure 2 is a side elevation of the rolling mill only, and

Figure 3 is a sectional view alon the line IIIIII in Figure 2.

Figure 4 is a block schematic of the electrical control system which can be utilised with either embodiment, and

Figure 5 is a similar view to Figure 2 of the die stand of the second embodiment.

Referring now to the drawings and to Figures 1 to 3 in particular, the apparatus of the first embodiment which is designed for the production of metal strip comprises a cold rolling mill Ill and reels H and i2 driven by electric motors l3 and i l. The rolling mill H3 is generally of conventional form comprising work rolls [5, supported in upper bearing chocks I 5 and lower bearing chocks ll respectively, and roll adjusting screws It. The mill in is, however, modified from conventional form by the interposition of steel cylinders l9 between each checks is and their associated adjusting screws it. A number of electrical resistance strain gauges 2B are secured around the side of the cylinders l9 and electric current from a control box 2! is passed through the gauges 29 via the connecting lead 22.

In this way the cylinders 59- act as pressure Sensitive elements as any variation in the pressure applied to them causes a variation in the electric current passing through the gauges 20.

The control box 2! contains the electronic equipment shown in the block schematic of Figure 4 and to be described hereafter. The purpose of the control box 25 is to feed a control current over the connecting lead 23 to the reel motor [4 in order to vary its torque.

In operation the strip 24 is unwound from reel H and is drawn through the work rolls l5 onto the reel I 2. The reels l I and I2 are driven at such relative speeds that tension is applied to the strip of the two upper bearing leaving the work rolls l5 and the amount of this tension depends upon the torque which the reel motor [4 develops. The roll pass and the tension, that is the torque of the motor 14, are adjusted to give a desired value for the outgoing thickness of the strip. Now any variations thereafter in the separating force between the rolls, which will result in a corresponding variation in the outgoin thickness, causes a change in the electric current passing through the gauges 20. The electronic equipment in the control box 2| is set so that these variations in the gauge current cause a corresponding variation in the output control current to the motor l4 such that the tension applied to the outgoing strip is varied to restore the separating force to its original value. In this way the tension in the strip is automatically continuously adjusted to maintain the separating force between the rolls as nearly as possible constant thus ensuring that the outgoing strip is of substantially uniform thickness along its length.

In its simplest form the electronic equipment may be merely a direct current amplifier for amplifying the current through the gauges to provide an amplified control current which is added to a fixed current, the combined currents being fed to the armature of the reel motor. However, it is preferred to use a circuit such as that shown in Figure 4. In this circuit the current from the gauges is passed through a discriminator which is arranged to give zero output when the roll separating force corresponds to the desired thickness of strip. Fluctuations on either side of this separating force lead to an output whose polarity depends upon whether the separating force is above or below the desired value, and this output is fed to a phase sensitive amplifier 25 and a direct current amplifier 21 whose output is added to a fixed current from a supply 28, the combined currents being fed to the armature 29 of the reel motor M.

In the second embodiment the cold rolling mill I0 is replaced by the die stand 30 shown in Figure 5, but otherwise the arrangement is similar to that already described. The die stand 30 has separate upper and lower lips 3|, 32 respectively of steel, metal carbides or other suitable hard material. The lower lip 32 is supported in a holder block 33 which is fixed to the die stand 30, whilst the upper lip 35 is carried in a holder block 34 which is vertically movable in the die stand 30 and can be pressed towards the lower lip 3! by the adjusting screws 35. In a similar manner to the rolling mill, cylinders 59 carrying strain gauges 20 are interposed between the holder block 34 and each adjusting screw 35. It will be readily understood that the separating force between the opposing die surfaces can be maintained substantially constant by adjustment of the tension applied to the strip in the manner already described for the first embodiment.

Although in the above described arrangements the pressure sensitive element has been arranged to produce electrical signals varying in accordance with variations in the separating force, it will be understood that alternatively mechanical or hydraulic means may be used for controlling the tension in the strip.

The following tables of experimental results show the improved control of thickness which is possible by means of the invention. The thickness measurements were taken at various intervals along the strip before and after rolling, and table (a) shows the results without control whilst table (b) shows the results using thickness control according to the invention.

Variation in thickness along strip (a) WITHOUT GAUGE CONTROL Before Rolling After Rolling Change in Thwtmess thickness Thickness if m at given between at Same t 10 ness intervals given intervals between along strip, intervals inches intervals, inches inches inches (11) WITH GAUGE CONTROL ACCORDING TO INVENTION It will be seen from the fourth column of figures that whereas the thickness varied over a range greater in the case where thickness control was used.

What we claim is:

1. In apparatus for reducing the thickness of material, a thickness reducing member having opposed material engaging surfaces, means for applying tension to the material, means for producing an output signal whose instantaneous magnitude is proportional to the force established between said opposed material engaging surfaces,

' and means for applying the output signal to the tension applying means to vary the tension applied to the material, whereby the thickness of the issuing material is maintained substantially constant.

2. In apparatus according to claim 1, a supporting stand in which said thickness reducing member is mounted, and a member mounted in said stand, and wherein said means for producing an output signal comprises a stress responsive member interposed between one of said opposed material engaging surfaces and said member mounted in said stand, an electrical resistance strain gauge mounted on said stress responsive member and responsive to variations in the compressive stress applied to said stress responsive member, and mean for applying an electric potential to said strain gauge, the resultant electric current through said strain gauge providing the required output signal.

3. In apparatus for reducing the thickness of material, a thickness reducing member having work engaging surfaces adapted to engage opposite sides of the material, a first material storage reel from which said material is drawn, a second material storage reel onto which said material is drawn after passing through said reducing member, means for controlling the torque of at least one of the storage reels for producing a tension in the material passing between the reels, means for generating a control signal whose instantaneous magnitude is proportional to the force established between work engaging surfaces, and means for applying said control signal to the means for controlling the torque of a storage reel, whereby the tension produced in said material is varied to maintain substantially constant the thickness of the material leaving said reducing member.

4. Apparatus according to claim 3, wherein said means for controlling the torque of said one of the storage reels comprises an electric motor to which said signals are applied to develop the required variations in the applied tension.

5. Apparatus according to claim 3, wherein said reducing member comprises a rolling mill, said work engaging surfaces being the work rolls of said mill, and said mill having adjusting members for setting the separation between said work rolls to a desired value.

6. Apparatus according to claim 5, wherein said means for generating a control signal includes a stress responsive member interposed between a work roll and an adjusting member, and electrical means responsive to variations in the stress produced in said stress responsive member for producing said control signal.

7. In apparatus for reducing the thickness of material by drawing it through a reducing member having opposed material engaging surfaces, means for applying a variable tension to said material, means for generating an electrical signal whose amplitude at any given time is proportional to the separating force existing at that time between said opposed material engaging surfaces, and means energized by said electrical signal to adjust the tension applied to said material by said first mentioned means to maintain said separating force substantially constant.

8. Apparatus according to claim 7, in which the means for generating an electrical signal proportional to the separating force includes a member engaging one of said material engaging sur faces, said member being stressed in proportion to said separating force, an electrical resistance strain gauge mounted on said member to respond to variations in the stressing of said member, and means for passing an electric current through said strain gauge.

9. In a rolling mill for reducing the thickness of material, a roll stand, opposed work rolls mounted in said stand, two adjusting members mounted in said stand for adjusting the separation between said work rolls, compressive-stress responsive means interposed between a work roll and each adjusting member, two electrical resistance strain gauges, one strain gauge mounted on each compressive-stress responsive means, means for applying an electric potential to said strain gauges to produce a current through said gauges which varies in proportion to the variations in the force applied to said adjusting members by the work rolls, a first material storage reel from which said material is drawn, a second material storage reel onto which said material is drawn after passing through said Work rolls, means for controlling the torque of at least one of the storage reels for producing a tension in the material passing between the reels, and means for applying said varying current to the means for controlling the torque of a storage reel, whereby the thickness of the material issuing from said work rolls is maintained substantially constant.

10. Apparatus according to claim 9, wherein said means for controlling the torque of said one of the storage reels includes an electric motor to which said varying current is applied to produce the required variations in the applied tension.

References Cited in the file of this patent UNITED STATES PATENTS Great Britain Aug. 5, 1938 

